It is known to sterilize packaging elements of the aforedescribed type in conjunction with the packaging of foodstuffs and the like, by passing the packaging elements in spaced relation through a sterilizing chamber and contacting them with hydrogen peroxide in a vapor state.
Referring herein to hydrogen peroxide vapor will be understood to include a hydrogen peroxide spray in which the hydrogen peroxide is in an aerosol or fine-droplet form with the droplets being in suspension in a carrier gas.
Sterilization of this type is described, for example, in German open application DE-OS No. 23 10 661.
In the preferred construction of this system, the stacked receptacles are displaced by a horizontally-moving belt conveyor from an inlet into the sterilizing chamber individually. A chain conveyor displaces the receptacles in a horizontal direction through the sterilizing chamber and a drying chamber downstream thereof to the filling and package-closing machine.
During the advance of the individual receptacles through the sterilizing and drying chambers, the stacked receptacles are engaged at their edges by grippers and are maintained at a constant distance or spacing from one another. The grippers are provided on the chain conveyor which is disposed beneath the receptacle stack.
The gripper devices of this system are formed with recesses transverse to the displacement direction and are in such manner that each gripper engages an edge of a respective receptacle and thus can transport it in the direction of movement of the conveyor.
Because of the one-sided engagement by the gripper devices with the edges of the receptacles, it is possible for the receptacles which are separated from one another to tilt or cant so that a part of one receptacle will contact a portion of a subsequent or preceding receptacle and uniform sterilization cannot be guaranteed because of such contact.
In a highly general way, it is state of the art also to allow receptacles to pass through a sterilizing chamber in a vertical direction. In these state of the art systems, however, the receptacle is open downwardly and it is likewise not possible to prevent, with such earlier systems, the partially separated receptacles of the stack from tilting or canting during their movement so that a part of one receptacle can come into contact with a part of another receptacle and again prevent uniform and complete sterilization.
Consequently, whether or not the receptacles are moved in the horizontal direction or in the vertical direction through the sterilizing chamber, there is the aforementioned disadvantage of the possibility of contact with interference with effective sterilization.
These systems also have other drawbacks.
For example, the conveyors will usually have one end extending into the sterilizing chamber and another end continuously outside the sterilizing chamber and creating a danger of reinfection.
A chain conveyor within the sterilizing chamber, moreover, in constant contact with the hydrogen peroxide and within the drying chamber in constant contact with hot air suffers a relatively significant temperature loading which can result in length changes in the conveyor chain and breakdown or the need for substantial maintenance. Indeed length changes may interfere with the ability of a transfer device downstream of the drying chamber to synchronize with the chain and transfer the packaging elements to the conveyor of the package filling and closing machine.
Generally also, a chain conveyor must be lubricated with a sterile lubricant and such lubricants tend to break down in the presence of hydrogen peroxide.
Mention can also be made of a receptacle-displacing system which utilizes conveyor screws and, specifically, three horizontally-arranged conveyor screws disposed equidistantly about the receptacles. The synchronously-rotated conveyor screws displace the receptacles with a constant spacing between them in a horizontal direction through the sterilizing and drying chambers.
Apart from the systems described which sterilize the packaging elements externally of the filling and package-closing machine, there are package-filling and closing machines which have the packaging-material sterilization integrated therein.
In these sterilizing systems utilizing hydrogen peroxide, the cups on a horizontally circulating conveyor belt are subjected to treatment with the H.sub.2 O.sub.2 vapor along their inner surfaces in sterilizing and drying chambers integrated into the machine along the transport path.
The H.sub.2 O.sub.2 vapor deposit has a fine condensate film on the inner wall of the receptacle so that fine, uniform wetting of the surface without droplet formation can be achieved. In a plurality of further stations downstream of the peroxide treatment station, the cups or receptacles are dried with hot air. The residual peroxide vapor in the exhaust hot air is drawn away by a blower.
The sterilized cups pass from the sterilizing chamber via specially constructed guide plates which also close off the sterilizing chamber and pass into the highly sterile compartment beneath the metering station at which the substance to be packaged is fed in unit doses or quantities into the sterile cups.
The lids for the cups are sterilized in a second sterilization chamber in accordance with the same principles.
With such integrated packaging-machine sterilization, the aforedescribed problems with H.sub.2 O.sub.2 loading and temperature loading of the transport chain are especially pronounced. In addition, since the sterilization and drying take place while the cups are moving horizontally and the sterilization chamber and drying chambers must be located horizontally along the conveyor, the overall length of the integrated packaging and sterilization machine and especially the part thereof upstream from the filling station may be intolerable because of spacial requirements.